1. Field of the Invention
The present invention relates to a semiconductor device capable of wireless communication.
2. Description of the Related Art
In recent years, development of a semiconductor device which can transmit or receive data wirelessly has been proceeding, and has attracted attention. A semiconductor device capable of wireless communication which is called an RFID (radio frequency identification), an RF chip, an RF tag, an IC chip, an IC tag, a wireless chip, a wireless tag, an electronic chip, an electronic tag, a wireless processor, a wireless memory, or the like, is beginning to be introduced to a part of market for a purpose of stock management. Desired features of the semiconductor device for goods management are compact, lightweight convenient, high-security, and inexpensive. In addition, a semiconductor device capable of wireless communication like this is mounted, for example, on a card, and applications for various fields are considered.
A semiconductor device capable of wireless communication which is in practical use now has an antenna layer and an element formation layer having a circuit which is configured with a transistor. Such a semiconductor device capable of wireless communication communicates with a reader/writer wirelessly via electromagnetic waves, whereby data is transmitted and received to and from the reader/writer, or electric power which is necessary for the operation of a semiconductor device is received from the reader/writer whereby the semiconductor device is operated.
Although a semiconductor device capable of wireless communication can be reduced in size and weight, the communication distance and the amount of supplied electric power can be changed by various factors. Therefore, size reduction is not always possible. In particular, influence of the shape of an antenna is significant.
A semiconductor device capable of wireless communication can be classified into some sorts depending on frequency bands to communicate. These semiconductor devices capable of wireless communication have features and they are selected for the purpose of use. The shape of an antenna may be changed in each time, or one chip may be provided with a plurality of antennas in order to ensure the communication distance and electric power in each frequency band. Reference 1 (Japanese Published Patent Application No. 2006-295729) is an example of one chip provided with a plurality of antennas.
In addition, many semiconductor devices capable of wireless communication now in practical use are so-called passive type which does not have a built-in battery but is supplied electric power from the external to operate, and the passive type is major. On the other hand, active type is also developed and examined to come into practical use. Further, semi-active type having a battery to which electric power is supplied wirelessly is also developed.